import pymysql

connection = None
cursor = None

try:
    # 1.建立连接
    connection = pymysql.connect(host="localhost",
                                 port=3306,
                                 user="root",
                                 password="123456",
                                 database="test_db",
                                 charset="utf8"
                                 )

    # 2.建立游标
    cursor = connection.cursor()

    # 3.执行sql语句, 查询employees表
    cursor.execute("select * from employees")

    # 4.游标取数据
    # 4.1 获取第一条数据
    re = cursor.fetchone()
    print("第一条数据是：", re)

    # 4.2 获取前两条数据
    cursor.rownumber = 0  # 游标位置归零
    re = cursor.fetchmany(2)
    print("前两条数据是：", re)

    # 4.3 获取全部数据
    cursor.rownumber = 0  # 游标位置归零
    re = cursor.fetchall()
    print("全部数据是：", re)

    # 4.4获取第三条和第四条数据
    cursor.rownumber = 2  # 游标位置归2，游标从0开始
    re = cursor.fetchmany(2)
    print("第三条和第四条数据是：", re)
except Exception as e:
    print("查询语句执行出错：", e)
finally:
    # 5.关闭游标
    cursor.close()

    # 6.关闭连接
    connection.close()